Topic: 403 to 455 swap interchanble parts.

[Hotrod028]

Hello Everyone! I'm new here and looking for wisdom. I own a 78 T/A Y-88 T-top,with a 403 Olds and a TH-350 trans.The rear end is a Posi unit with stock 3.21 gears.This was the very first car I bough and it's has been in a coma for the last 7 years. I'm going to swap the motor for a 71 455 Pontiac motor. My question is how much of the 403 parts like engine mounts, accessories brakes can be reused. Also, can the air filter housing from the Olds  be used on the Pontiac with out relocating the shaker? My intentions is to make it a street/strip car.

[TAKID455]

Nothing. All is different.   Engine bay wiring can be made to wok though.

[Grand73Am]

True that there's not much that is interchangeable from a Olds 403 to a Pontiac engine. You can use the th350 transmission on the Pontiac. And the starters are the same. That's about all.
You can use the 403 motor mounts that are on the frame, since those are same whether you use the 403 or the Pontiac engine. But you can buy those new and they're cheap. What you will need to mount the Pontiac engine in your 78 TA are the engine mounting brackets. These are the brackets that bolt to the engine and then sit over the motor mounts on the frame. You have to find some Pontiac engine mounting brackets that came off of a Pontiac engine that was in a 75-81 Firebird or TA. The brackets can be from 400, 455, or even a 301 Pontiac engine, but only if the engine was in a 75-81 Firebird or TA. No other brackets will work. The part numbers that are stamped on the brackets are 496892 for the right side, and 496893 for the left side.
Then you'll need all the engine pulleys, alternator brackets, p.s. brackets and pump, and a/c brackets for the Pontiac engine. And it would be best to find a Quadra-Jet carb from a 76-79 Pontiac engine to use.
The brakes remain the same.
You'd need an air cleaner and shaker from a 77-79 TA with Pontiac 400 engine, if you want it to fit without any work. This thread at TAC shows the difference between a 403 air cleaner and shaker and a Pontiac 400 (or 455) air cleaner and shaker:  http://transamcountry.com/community/index.php?topic=34280.0

[Hotrod028]

Thanks for the info, that will get me started on the missing parts . The motor is a 71 455 Pontiac 2 bolts main. It came with an Edelbrock Torker II intake, the alternator, p.s. brackets and respective pulleys. It also have  the distributor and the engine mounts. The previous owner had the motor on a 78 T/A like mine, so at least I have that cover. For the carburetor I'm planning to used the Edelbrock manual choke that it was with the 403 since is in good shape.
 One thing that I notice on the 455 is that the oil press switch is on the oil filter bracket and no on the front of the engine like the 403.

[mikekop]

There was only 880 Y88 made with the 403/auto combo. Keep it stock.

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[Hotrod028]

It was my intention to build the original 403 but the motor had another idea and broke. I'll keep the motor stash away if I later decide to fix it and bring it to original state. the Poncho motor is a better idea for the plans I'm going after.



 

[mikekop]

Sure, do what you want. I guess the other owners of stock Y88:s with the 403 will be happy, because if yet another one gets hacked up it will make theirs more valuable and rare.

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